and even if I have Mojave or High Sierra? I can't since I can't get the installer, which is the gist of the problem.
PERPETUAL v6 DOWNLOAD
ProDesign Tools kindly offers a download link that is for Lr v6.14 (Perpetual)- There is no telling how much longer Adobe will allow this to work. It is the only source now for v6.14
https://prodesigntools.com/adobe-lightroom-6-cc-direct-download-links.html

Time you considered the Photography Plan that will upgrade you to v11 of Lightroom-Classic. ($9.99 PHOTOGRAPHY PLAN (USA)
Lr v6.14 is now well past End-of-Life! No support is available from Adobe. Lr v6.14 cannot be installed on any Mac OS later than Mojave. Windows-11 unknown compatability! Several functions in Lr6.14 now do not work- (Maps, Face recognition).
Activation reset (for maximum 2 installs) is becoming very difficult and can only be done by Adobe Staff via a Chat box. You need to be logged in and allow cookies in your Browser. You must ask ONLY for “Activations Reset”. If you ask for “Support” there is no answer.
https://helpx.adobe.com/contact.html?rghtup=autoOpen
v6 is Falling Apart- Petapixel article