Actually because Elon. Really.
The act requires a certain market position from a company. Which Twitter once definitely had - but does no longer have. A lot of companies have turned their back on Twitter due to Musk (not only advertising wise but especially communication wise). And that does reduce the impact it possibly can have on the market. (Remember: The DSA is a market equalisation act)
OPNsense on any small scale dual LAN box, either a used mini PC or a purpose made one.