I was looking at browser compatibility for early-2010s machines earlier; doesn't Firefox go further back than Chrome? Firefox says it will support 10.12 (Sierra)...
Yes, but my family prefers Chrome, as do I. It's more versatile and compatible. We do have Firefox installed though.
That being said, in this case, there's the Intel vs ARM question. Will folks like Google want to support Intel Macs for 5 years after Apple?
I'm not getting the impression anyone wants to forget about Intel as quickly as folks wanted to forget PowerPC, but when you hear that M2 Pro MBPs are apparently 7X faster than 2017 Intel 13.3" MBPs, there may be a tipping point and Intel gets promptly forgotten after that tipping point is reached.
I am not a developer, but it seems to me they will support Intel Macs as long Apple supports them in the latest version of Xcode. All they have to do is keep building the fat binaries that Xcode supports. And given that Apple STILL sells Intel Macs, I suspect Apple will continue to support Intel in Xcode for a very, very long time. In the very least it would be 2028, but it's likely going to be much longer than that.
As for Google, their concern is not speed, but installed base. Just the fact that Apple Silicon is way faster doesn't negate the fact that there many, many, many more Intel Mac users out there than Apple Silicon Mac users out there. If speed really mattered they probably wouldn't be supporting 10.13 High Sierra right now. Ultimately, browsing doesn't really take
that much speed. My fanless 2017 12" MacBook still browses just fine for example. It's really mainly about RAM. It's fine as long as you have at least 8 GB RAM.
EDIT:
P.S. In my opinion, any machine with at least 8 GB RAM and which has a Geekbench 5 single-core score of around 600 or better along with a multi-core score of about 1400 or better, surfs full desktop websites fine in 2023.
750/1550 - 2017 13" MacBook Air (Core i5-5350U)
780/1590 - 2017 12" MacBook (Core m3-7Y32)
760/1650 - 2014 Mac mini (Core i5-4278U)
800/1720 - 2015 13" MacBook Pro (Core i5-5257U)
610/2225 - 2010 27" iMac (Core i7-870)
We have all of these machines, and have no complaints about any of them for surfing speed. Is my M1 Mac mini way faster? Yes, no comparison at 1750/7800, but for web browsing, it's diminishing returns.
Will most of those machines seem slow surfing in 2028? Probably, but they will likely still work fine for light users, and Google will still want to capture those users to harvest their surfing data of course.
Ironically, I think the only machine in the above list that will likely lose Chrome support sooner rather than later is the fastest Intel Mac above, which is the 2010 Core i7 iMac, because it's stuck on 10.13 High Sierra. The other slower machines will still continue to receive Xcode support from Apple for longer, as they all run at least Monterey or later.