I don't think that is a Firefox issue but Microsoft issue I've read users of Windows 7 installing the latest Firefox AFAIK and used it without issues? This is a question that is best directed to Windows O/S support.

There is a bug for dropping support for Windows 7 where there is also some mention of Windows 8, but no mention of dropping support for Windows 8/8.1

• 1594270 - (win7-eol) [meta] Remove support for Windows 7

(please do not comment in bug reports
https://https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

See also;

• https://support.mozilla.org/en-US/kb/import-bookmarks-internet-explorer-or-microsoft-edge
• https://support.microsoft.com/en-us/office/windows-8-and-windows-8-1-end-of-support-and-office-34e28be4-1e4f-4928-b210-3f45d8215595

Answers almost like a pass the buck smokescreen. This is a little about windows, but mainly, will mozilla keep the browser upgrading support for older operating system into 2023-2025 & beyond, regardless of what Microsoft do.

I'm not aware if there is already a decision made about stopping support for Windows 8 version, but there can still be an internal discussion about for how long to keep supporting this OS.

In the past when support for an OS ended the users were moved to the current ESR version to offer them at least security updated until ESR moved to the next major version. ESR is currently 102 and 102.15.0 will be the last version. If the next ESR version (115) still supports Windows 8 then support will be extended for another year.

• https://wiki.mozilla.org/Release_Management/Calendar

Chrome 109 is the last version of Chrome that will support Windows 7 and Windows 8/8.1. Chrome 110 (tentatively scheduled for release on February 7th, 2023) is the first version of Chrome that requires Windows 10 or later. This means Chromium will be dropping support of Windows 7 and Windows 8/8.1 then also.

The Vivaldi browser will also be ending support of Windows 7 and Windows 8/8.1 then also. https://vivaldi.com/blog/pulling-the-plug-on-expired-operating-systems/

The Brave browser will be ending support for Windows 7 and Windows 8/8.1 starting in early 2023 with the release of Brave version 1.47.x (Chromium 109). https://support.brave.com/hc/en-us/articles/11197967945613-Sunsetting-support-for-Windows-7-and-8-8-1

Unless Mozilla extends support for Fx 102 ESR the last major update Fx 102.15 ESR is planned for at end of August 2023. Will they extend support to Fx 115 ESR we will see.

Mozilla supported the EOL WinXP (and Vista) til Fx 52.9.0esr released June 26, 2018. Over two years after Chromium, Chrome, Opera dropped WinXP/Vista support back in April 2016.

Anybody still using a old 32-bit CPU is more out of luck as using Linux as a alternative OS will be more tricky as time goes on as 32-bit Linux distros become more scarce.