There's some truth to it, but it's mostly that junior developers and senior developers with no discipline that give it a bad name.

The major problem is that it has one of the the highest capacities for writting incredibly dense code there is, paired with very powerful language transformation tooling (i.e. switch statements were added as a module, but can also be used for funny evil.)

Yes! I actually had this exact desire years ago, and went searching for it. RegexBuddy does this, best $US 40 I've spent. It'll even do its best to make something that'll match the same things, even if you're using features that aren't technically supported in the target. Don't worry, it'll describe exactly what doesn't work, and why, when it does that.

For example, if I ask it to convert from C# /(?>atomic) case-(?i)insensitive(?-i) string/ to JavaScript (chrome) it'll throw out: /(?:atomic) case-[iI][nN][sS][eE][nN][sS][iI][tT][iI][vV][eE] string/, along with the warning:

Conversion is incorrect because the target application's regular expression flavor doesn't have certain features: JavaScript (Chrome) does not support atomic grouping

MathNet.Numerics has a pretty solid linear systems solver, and has multiple additional native providers that, depending on what hardware you have to work with, and the size of your solves, dramatically increases performance.

You could... but it's singly not setup for that. There are blog softwares out there that support activitypub-- I have no experience with it, but microblog.pub was nativity designed as an activitypub blog. There's also a WordPress plugin that's basically official (maintained by the company that owns WordPress.com) and has known good integration to at least mastodon, so I would assume it works well with lemmy, peertube, etc, since AFAICT, mastodon is the most opinionated of them when it comes to activitypub conformance.