How's the performance of Gmail on the Celeron? That's always my sticking point for older computers. The fancy web applications really drag.
Not great. Works well with Thunderbird or Evolution though.
And yes. Web apps are not really great on low-spec machines.
I still use Ivy Bridge and Haswell workstations (with Linux, SSD and discrete GPU) as my daily drivers and for the things I do they still feel fast. Honestly a new Celeron probably beats them performance wise.
The modern AMD or Intel desktops I've tried obviously are much faster when performing large builds and such but for general computing, web browsing, and so forth I literally don't feel much of a difference. Now for mobile devices it's a different story due to the increased efficiency and hence battery life.
I am due to update my Mac mini because my current one can't run Sonoma, but, apart from that, it's a lovely little box with more than enough power for me.