P: Slow UI when using Mac and Custom Display Profile

Try reducing the resolution of the UI in Lightroom by navigating to the Adobe Lightroom Classic.app in the Finder, and then click on "Get Info."  Check the box to "Open in Low Resolution."  This will allow the UI, including the text in the side panels etc.  to open in low resolution (without affecting the resolution of the image display).  It's worth a shot.  I've been using LRC like this for quite a while and it does seem to improve performance a bit.  And I don't really care if the text is in lower resolution as it is still easy to read.

Mac Users: try giving your Mac the "once over"! It may be a corrupt cache or application state that needs deletion:

Download the free Onyx (https://www.titanium-software.fr/en/onyx.html), select the Onyx version for your OS, download, run it, reboot.

In Onyx run almost everything in the Maintenance tab, deselecting things you may not want deleted, like Launch Services . Hit the "Options" button across from "Internet" and check/deselect more stuff like Cookies & Other Site Data, Browser History, Form Values, (which are OFF by default), but make any other choices you want to keep. If you don’t know what something is, google it, or don’t run it, or ask me, then hit Run Tasks. After it's done it will ask for a reboot.

Also try to fix any directory damage by running Disk First Aid from Disk Utility: boot into Recovery Mode, (hold down Command-R when booting). When you're in Recovery Mode go to the Utilities menu and launch Disk Utility, select Macintosh HD (or whatever) and say Repair Disk. When done go to Apple Menu for Startup disk and restart normally.

Same issue here, hardware seems not the be the reason for the problem:

14-Core i9 10940x

128GB DDR4 RAM

AMD Radeon VII 16GB

Running 10.15 Catalina

New v10 Lightroom is very slow. Seconds after first start it was very fast, soon after everything started to slow. Even the curser lags. Activity monitor on MacOS shows huge CPU usage of LR even when idle.  

I'm running on macos 10.14.6 on a Mac Pro 5,1 with maxed out specs and a Radeon VII graphics card. My Lightroom library is quit large but this was no problem before. I switched back to version 9.x so I can use Lightroom again. Version 10 was not usable at all, freezing all over the place.

I'm getting the same problem, latest OS but on a 2013 iMac (yes, I know its old but was working with Lightroom very well prior to the update.).

What was a simple task previously such as spotting out dust now beachballs for 2 or 3 minutes.

I would love to be able to recommend updating but Lightroom doesn't seem to be quite ready yet...

I am not. Like I said above my desktop rig with 3900X, 64GB ram, RTX2070Super with latest Win 10 works great. Dont know if its due Nvidia GPU in the PC or slower HW in MBP.

Here is my Lr System info: 

Lightroom Classic version: 10.0 [ 202010011851-ef6045e0 ]
License: Creative Cloud
Language setting: en-US
Operating system: Mac OS 10
Version: 10.15.7 [19H2]
Application architecture: x64
Logical processor count: 16
Processor speed: 2.4 GHz
SqLite Version: 3.30.1
Built-in memory: 32,768.0 MB
Real memory available to Lightroom: 32,768.0 MB
Real memory used by Lightroom: 2,618.7 MB (7.9%)
Virtual memory used by Lightroom: 32,387.7 MB
Memory cache size: 2,251.3MB
Internal Camera Raw version: 13.0 [ 610 ]
Maximum thread count used by Camera Raw: 5
Camera Raw SIMD optimization: SSE2,AVX,AVX2
Camera Raw virtual memory: 1564MB / 16383MB (9%)
Camera Raw real memory: 1632MB / 32768MB (4%)
Displays: 1) 6016x3384

Graphics Processor Info: 
Metal: AMD Radeon Pro 5500M

Application folder: /Applications/Adobe Lightroom Classic
Library Path: /Users/xxxxxxxxxx/Library/Mobile Documents/com~apple~CloudDocs/a_Lightroom/Master_Lightroom_Catalog/Master_Lightroom_Catalog-2 2-v10.lrcat
Settings Folder: /Users/xxxxxxxxxx/Library/Application Support/Adobe/Lightroom

Installed Plugins: 
1) AdobeStock
2) Aperture/iPhoto Importer Plug-in
3) Facebook
4) Flickr
5) Nikon Tether Plugin
6) Smart Shooter 4

Config.lua flags: None

AudioDeviceIOBlockSize: 512
AudioDeviceName: $$$/dvaaudiodevice/SystemDefaultAndEffectiveDeviceName=System Default (MacBook Pro Speakers)#{comment}DVAAU-4201250: Open the audio hardware preferences page.
AudioDeviceNumberOfChannels: 2
AudioDeviceSampleRate: 48000
Build: LR5x42
CoreImage: true
GL_ACCUM_ALPHA_BITS: 0
GL_ACCUM_BLUE_BITS: 0
GL_ACCUM_GREEN_BITS: 0
GL_ACCUM_RED_BITS: 0
GL_ALPHA_BITS: 8
GL_BLUE_BITS: 8
GL_DEPTH_BITS: 24
GL_GREEN_BITS: 8
GL_MAX_3D_TEXTURE_SIZE: 16384
GL_MAX_TEXTURE_SIZE: 16384
GL_MAX_TEXTURE_UNITS: 8
GL_MAX_VIEWPORT_DIMS: 16384,16384
GL_RED_BITS: 8
GL_RENDERER: AMD Radeon Pro 5500M OpenGL Engine
GL_SHADING_LANGUAGE_VERSION: 1.20
GL_STENCIL_BITS: 8
GL_VENDOR: ATI Technologies Inc.
GL_VERSION: 2.1 ATI-3.10.18
OGLEnabled: true
GL_EXTENSIONS: GL_ARB_color_buffer_float GL_ARB_depth_buffer_float GL_ARB_depth_clamp GL_ARB_depth_texture GL_ARB_draw_buffers GL_ARB_draw_elements_base_vertex GL_ARB_draw_instanced GL_ARB_fragment_program GL_ARB_fragment_program_shadow GL_ARB_fragment_shader GL_ARB_framebuffer_object GL_ARB_framebuffer_sRGB GL_ARB_half_float_pixel GL_ARB_half_float_vertex GL_ARB_imaging GL_ARB_instanced_arrays GL_ARB_multisample GL_ARB_multitexture GL_ARB_occlusion_query GL_ARB_pixel_buffer_object GL_ARB_point_parameters GL_ARB_point_sprite GL_ARB_provoking_vertex GL_ARB_seamless_cube_map GL_ARB_shader_objects GL_ARB_shader_texture_lod GL_ARB_shading_language_100 GL_ARB_shadow GL_ARB_shadow_ambient GL_ARB_sync GL_ARB_texture_border_clamp GL_ARB_texture_compression GL_ARB_texture_compression_rgtc GL_ARB_texture_cube_map GL_ARB_texture_env_add GL_ARB_texture_env_combine GL_ARB_texture_env_crossbar GL_ARB_texture_env_dot3 GL_ARB_texture_float GL_ARB_texture_mirrored_repeat GL_ARB_texture_non_power_of_two GL_ARB_texture_rectangle GL_ARB_texture_rg GL_ARB_transpose_matrix GL_ARB_vertex_array_bgra GL_ARB_vertex_blend GL_ARB_vertex_buffer_object GL_ARB_vertex_program GL_ARB_vertex_shader GL_ARB_window_pos GL_EXT_abgr GL_EXT_bgra GL_EXT_bindable_uniform GL_EXT_blend_color GL_EXT_blend_equation_separate GL_EXT_blend_func_separate GL_EXT_blend_minmax GL_EXT_blend_subtract GL_EXT_clip_volume_hint GL_EXT_debug_label GL_EXT_debug_marker GL_EXT_depth_bounds_test GL_EXT_draw_buffers2 GL_EXT_draw_range_elements GL_EXT_fog_coord GL_EXT_framebuffer_blit GL_EXT_framebuffer_multisample GL_EXT_framebuffer_object GL_EXT_framebuffer_sRGB GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters GL_EXT_gpu_shader4 GL_EXT_multi_draw_arrays GL_EXT_packed_depth_stencil GL_EXT_packed_float GL_EXT_provoking_vertex GL_EXT_rescale_normal GL_EXT_secondary_color GL_EXT_separate_specular_color GL_EXT_shadow_funcs GL_EXT_stencil_two_side GL_EXT_stencil_wrap GL_EXT_texture_array GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc GL_EXT_texture_env_add GL_EXT_texture_filter_anisotropic GL_EXT_texture_integer GL_EXT_texture_lod_bias GL_EXT_texture_mirror_clamp GL_EXT_texture_rectangle GL_EXT_texture_shared_exponent GL_EXT_texture_sRGB GL_EXT_texture_sRGB_decode GL_EXT_timer_query GL_EXT_transform_feedback GL_EXT_vertex_array_bgra GL_APPLE_aux_depth_stencil GL_APPLE_client_storage GL_APPLE_element_array GL_APPLE_fence GL_APPLE_float_pixels GL_APPLE_flush_buffer_range GL_APPLE_flush_render GL_APPLE_object_purgeable GL_APPLE_packed_pixels GL_APPLE_pixel_buffer GL_APPLE_rgb_422 GL_APPLE_row_bytes GL_APPLE_specular_vector GL_APPLE_texture_range GL_APPLE_transform_hint GL_APPLE_vertex_array_object GL_APPLE_vertex_array_range GL_APPLE_vertex_point_size GL_APPLE_vertex_program_evaluators GL_APPLE_ycbcr_422 GL_ATI_blend_equation_separate GL_ATI_blend_weighted_minmax GL_ATI_separate_stencil GL_ATI_texture_compression_3dc GL_ATI_texture_env_combine3 GL_ATI_texture_float GL_ATI_texture_mirror_once GL_IBM_rasterpos_clip GL_NV_blend_square GL_NV_conditional_render GL_NV_depth_clamp GL_NV_fog_distance GL_NV_light_max_exponent GL_NV_texgen_reflection GL_NV_texture_barrier GL_SGI_color_matrix GL_SGIS_generate_mipmap GL_SGIS_texture_edge_clamp GL_SGIS_texture_lod 

After years of complaining about how slow LR Classic is, the latest 2021 update brought me great joy... at least for the first two sessions I was using it. It was flat out peppy! Images were opening fast, going through the pick process was moving at a rapid clip. 

Then today, the third session I'm using LR Classic 2021, it's BOGGED down slow. Slower than 2020 previously. I restarted the computer, left all other apps closed, and same speed behaviors. 

I am running the latest MacOS Catalina 10.15.7 and have made no OS or software updates after updating LR Classic to 2021 version. 

I'm running on a 2019 MacBook Pro laptop with no other issues of any kind. 

Is anyone having these problems on a Windows machine? If this is strictly macOS, that will help the Lightroom developers isolate the issue. 

@lewis_kemper 

I didn't read your question correctly, my mistake. I don't believe that Lightroom will work with an external GPU. Saw that posted somewhere but don't remember where it was.