OP specified they live in Northern Ireland so it is unlikely they will be able to get a job with an American defense contractor as a non-citizen who can't obtain a security clearance.
I live in Tucson and am quite familiar with Raytheon (having been recruited and know numerous employees as they are the biggest employer here). They are not going to be hiring remote developers from Ireland. In all likelihood, they will not be hiring any remote developers anywhere, unless those people will be relocating to Tucson and being on premise once this calms down.
Hmm. How are environments like this handling the WFH status quo?
My completely naive/distant presumption of sites like these is that they are fundamentally incompatible with the security concessions inherent to remote work.
They should have various tiers for security levels. What is often the challenge is that the most interesting work requires citizenship + clearance. Since OP is fine with rote work there might be some possibilities here.
I work for a government contractor on a tier of clearance far below what's used in defense, and we are not even allowed to take any US Gov't issued equipment outside of the US, much less actually work from there.
No way in hell anyone in Ireland is going to be doing US Gov't contracting work, unless they are on the US Embassy grounds.
Sorry. (Government contracting is exactly what the original recommendation describes..unglamorous but steady, FWIW)