Let’s go through ecpair first.
The error complains about this location: UNPKG - ecpair
As you can see, it’s a class field. And, unfortunately, GCC doesn’t support class fields yet: Add Support for Class Fields · Issue #2731 · google/closure-compiler · GitHub
I don’t know what the preferred way of fixing such an error is. Perhaps webpack could somehow be used. Or you might be able to vendor in the library. Or maybe use some older version of it that doesn’t use class fields - that was exactly what I did with ANTLR.
Regarding crawlee - that particular line is here: https://unpkg.com/browse/@crawlee/core@3.1.0/errors.js#L27
And the column points somewhere around ?? which is called “nullish coalescing operator”, which is supposed to be supported by GCC since v20200315. Is there a chance your CLJS version is out of date or you explicitly depend on an old GCC version? I just tried compiling a simple script that only requires ["crawlee"] and it worked just fine with shadow-cljs 2.20.4.