Need advice upgrading my LR5.7.1 to LR6 (or higher) on a different PC

Upgrade to Version 6 (Perpetual) - You cannot... Not worth chasing!

Basically only one option is open to you and that is to subscribe to the Photography Plan (20GB) to install Lightroom-Classic v13.  Check your computer compatibility here- ! Lightroom-CLASSIC System requirements 

There might be the possibility of converting your NEF fies to the DNG raw format with the Adobe DNG Converter App to use with Lr v5., but the DNG Converter also requires a recent version of the Windows OS.

DNG LEGACY SUPPORT

https://helpx.adobe.com/camera-raw/system-requirements/2021.html

There is NO upgrade from Lr 5 to Lr 6. There used to be, back when Adobe sold Lr 6, you would have to pay for the upgrade to Lr 6. But Adobe does not offer Lr 6 for sale any more, and hasn't for 6 or 7 years now. So the only upgrade you can do now is to subscribe to the current version of Lightroom Classic (which is version 13.1). Lightroom Classic is the direct successor to Lr 5, and your work in the Lr 5 catalog will be used by the LrC 13 catalog. To do this, you do not need your Lr 5 serial number, and there is no discount in the price of subscription to LrC because you have Lr 5.

Several issue. Let's start with the big one

1. Availability of old Lightroom pre subscription

Adobe no longer sells, provides, supports the old perpetual versions of Lightroom. Several years ago, Adobe decided to stop selling the software in the form of a CD, or a DVD, or even downloading an installer for the old perpetual software. Instead they went to subscription based.

see:

• https://robertreiser.photography/end-of-lightroom-as-we-know-it/
• https://www.dpreview.com/opinion/5431017013/rip-lightroom-6-death-by-subscription-model
• https://nikonrumors.com/2017/10/18/adobe-lightroom-cc-and-lightroom-classic-announced-d850-support-for-lightroom-6-will-come-on-october-26th.aspx/

At that time they produced Lightroom 6, ending in Lightroom 6.14. And at the same time Lightroom via subscription v6.14

They advertised that the old Lightroom would no longer be provided support, that the software was being sunseted.

Three years passed, after the sunset, and as such Adobe was able to legally stop all support.

Now as of the end of last month they have stopped providing a server for downloads of the old software.

see:

• https://helpx.adobe.com/lightroom-classic/help/lightroom-6-end-of-support.html
• https://www.lightroomqueen.com/lightroom-6-downloads-ending/

2. Ability to install old Lightroom software on a computer

If you have the CD or DVD, or just a download (before Adobe killed that) Then you might be able to install the old software on the new computer. HOWEVER, if it needs to be registered at Adobe, that may be a big issue. I forget what versions required that (it is a bit muddy)

You can try to contact ADOBE, and ask for an adviser/tech (as opposed to a auto chat) and plead for a license registration. But that is doubtful. Stress this  is for licensing to bug issues.

3. Ability to upgrade from v5 to v6 (Windows)

The Adobe site for downloading the software in question is no longer available. Other sources may or may not exist. Perhaps some other member still has one. This might be a bit legally troublesome.

4. Install on MACOS

The old software will not load in the new non Intel MACs is not possible. On non Intel MACs, if the MACOS is Catalina or newer, then the install for Lr 6 is a no go (32 bit installer, MACOS refuses 32 bit apps), Older that v6 might be possible on Intel MAC, but questionable.

5. Updates, Upgrades

For the perpetual Lightroom, not going to happen

6. What will not work

If you do manage to get Lr v6.14 perpetual installed, some features will not work, and the list of failures will probably increase. Most of these are due to services/links/licenses  that Adobe paid for but no longer wants to pay for when they are getting no income stream for Lr 6.14 users. For example, Face Detection.

see:

• https://petapixel.com/2020/12/24/adobe-lightroom-v6-is-falling-apart/

7. If you decide to subscribe

If you decide to subscribe, be very very carefully of what Adobe Plan you subscribe to. Old version lightroom users often see the Lightroom Plan.. Yep, I want Lightroom. Big mistake, that would only provide what is now called Lightroom Ecosystem (Cloud Based) a/k/a Lr cloudy, or to us old farts Lr POS. What you are used to is now called Lightroom Classic, currently v 13.1, Typically via the Photography Plan.

see:

• https://www.lightroomqueen.com/lightroom-cc-vs-classic-features/
• https://www.adobe.com/products/photoshop-lightroom-classic/lightroom-cc-vs-lightroom-classic.html
• https://www.adorama.com/alc/lightroom-classic-vs-lightroom-cc-whats-the-difference/

8 Workaround

If you have a working but out of date copy of Lighroom that does not support your camera. An alterrnative is to use a DNG converter (as long as that works on yur system). Both afvailoable from Adobe, and perhaps from the camera mfg. Sucha as:

https://www.lightroomqueen.com/lightroom-6-downloads-ending/

9. Windows OS compatability

I am a bit confused, Windows 7 or 10, or is that two computers?

As mentioned below, see the System Requirements for Lightroom Classic. Windows 10 OK, Windows 11 (if you can upgrade) better (semi pro tip, avoid being forced to use a MS account if you install Windows 11), but Windows 7, well that has issues.

see:

• https://helpx.adobe.com/lightroom-classic/system-requirements.html

If you look at the above link, notice the ability to look at earlier releases. Lightroom Classic v 9 may run on Windows 7. Now to actually get v9 requires a chat and call with Adobe, It is not available normally on-line. They would hopefully provide a link. But it would really really be time to dump Windows 7.