... On June 26th/27th, bloody Microsoft devs unleashed a set of newer-JS-syntax-containing GitHub scripts; "new" JS features included the dreaded Optional Chaining ("?.") and Nullish Coalescing ("??") operators, that can't be polyfilled (but, perhaps, could be transpiled...).
Fortunately for "us", very recent UXP-based roytam1 forks (e.g., I use myself St52 and, occasionally, NM28) have these two operators natively supported, thanks to the efforts of an "upstream" dev! ; of course, you need either the github-wc-polyfill (v1.2.19) or palefill (v1.14) extension in order for GitHub to be usable in UXP-based browsers, but, all things considered, latest Serpent 52.9.0 (and, probably, latest NM 28.10.6a1) survived these most recent GitHub changes practically unscathed...
Goes without saying that in browsers lacking such support (older UXP-based builds, Chromium forks based on Ch<80 - yes, these include both 360EEv11/v12 ), GitHub is basically now BROKEN (you can simply browse GitHub pages, but you can't do many "useful" things on them ...).
And here comes Serpent 55.0.0 ; after the recent "sync" with UXP (thanks roytam1), and for a brief period of several weeks, GitHub was fully functional in St55, provided, of course, gh-wc-polyfill/palefill had been force-installed there (neither of these two extensions cater "officially" for the moebius fork...).
AIUI, latest St55 [v55.0.0 (2022-06-22) (32-bit)] should have native support for both "?."+"??" operators, backported from UXP; however, after the recent GH changes, I find that GH is no longer usable there ; I have gh-wc-pf_v1.2.19 force-installed and many GH pages do work as expected, but other pages cause the browser to fully crash ; example is the main repo page of any GH project, e.g.
https://github.com/gorhill/uBlock
https://github.com/JustOff/github-wc-polyfill
etc., the issue tracker of a project will also, often, produce a crash and, last-but-not-least, trying to access your GH account via your avatar (top right) will ALWAYS result in a full-blown browser crash...
@roytam1 : Please, can you reproduce at your end?
Given that latest St52 doesn't suffer from this, does this mean you need to transfer more UXP "stuff" to moebius for GH to work, or is that no longer possible?
As I've posted in the past, GitHub is a site I use many times daily, I already lament the loss of proper support in 360EEv11/v12, I thought St55 would've been my third option besides St52+360EEv13, only to sadly find it, too, has been broken by Microsoft...