Older Macs and maximum macOS version

The discussion comes up from time to time on the dev forum or group whether or not to drop a particular variant of an OS, use an older variant of a development tool, especially when the current/latest version of one of the upstream development tools does not support the older version. This had to be done to get 3.0 Beta 2 working on macOS <10.12 but still leaves a question mark around 10.8 & 10.9 , e.g.

Anatoly-os: "QT 5.9 doesn't work for 10.7 (checked by @lasconic). It could work for 10.8 or 10.9, but indeed 'just' not supported by Qt officially."

Since Macs running these older versions of macOS (officially called Mac OS X / OS X “back in the day”) I decided to gather some field data of the various Mac models and the maximum macOS versions they support. There are sites out there that do this for you e.g.
https://everymac.com/systems/by_capability/maximum-macos-supported.html
https://eshop.macsales.com/guides/Mac_OS_X_Compatibility

I compiled my own list using MacTracker (iOS app). To keep thing simple, I
1 did not look at individual models, but the models in a year.
2 looked at the main model ranges only (iMac, MacBook, MacBook Pro), excluding MacBook Air, Mac Pro, Mac Mini, since the maximum macOS tend to correspond with the same year for all Macs released in the same year.
3 Only list years until reaching $LATEST (10.14 in 2018)

Sample output:
Year type max_macOS
2006 iMac 10.6/10.7
2007 iMac 10.11
2008 iMac 10.11
2009 iMac 10.11
2010 iMac 10.$LATEST
...
Full table available at
https://musescore.org/en/handbook/developers-handbook/versions-reference

Conclusion:
1 Some version like 10.7 and 10.11 seem to be some kind of Long Term Support, e.g. the in-between versions, 10.8-10.10 don’t feature at all. E.g. you will not get a Mac that only supports up to 10.9 as max macOS.
2 The only reason to support a non-”LTS” macOS (10.8-10.10) is not because the Mac does not support 10.11, but because the user can or does not upgrade (e.g. by choice, lack of know-how, performance, another application compatibility or access to the update)
3 iMac and MacBook Pro seem to be almost identical, e.g. 2007-2009 max macOS is 10.11.
4 Once support on the upstream toolchain drops support for 10.11 (and the MuseScore developers no longer release a binary with the older toolchain), it will impact a significant number of model years, 2007-2009

(disclaimer - I have a 2007 iMac running macOS 10.11, so I have a vested interest in said binary)

My question to users:
1 Are you still using macOS 10.8 or 10.9 (Apple logo -> About This Mac)
2 Would you be willing to test the latest 3.0 beta to see if it works, even if it is not officially supported / certified? (it is available at https://musescore.org/en/download Try out the beta release of MuseScore 3 -> Download for old Mac (macOS 10.7 - 10.11) and let us know if it works for you or not.
3 Are you still using macOS 10.7 ? There currently is no binary but depending on demand, the devs may or may not look into it.

ps: I am not a developer and cannot speak on behalf of them or MuseScore the company. This is just to try and get the discourse going, maybe help making an informed decision around support of MuseScore 3.0 for an old version like 10.7.