I’ve sort of solved it now by using Cloudflare. I have turned off the Cloudflare page rule for a while if you want to see the 404 happening.
Try this link as an example:
I added it like this in admin / settings / permalinks:

This is what it looks like once it’s added:
And the result is this:
I’ve tried with a trailing slash as well.
If I do the Cloudflare Page Rule to remove the fbclid stuff before it hits Discourse, then it works just fine.
Is this what the Discourse “Permalinks Normalization” is for? Would I be able to strip out anything after ? using that setting?

