For the best answers I would recommend contacting the Support team via this page.
What I’ll say is that once a major release comes out, there are almost never hotfixes for older releases. Currently we are on UE 5.4.3. You should not expect additional hotfixes for 5.3. The roadmap continues to move onward and a new major release is roughly every 6 months or so. I don’t know if that completely satisfies your definition of “support” which is why it might be better to look at the options on that support page.