Ask HN: What is the danger of using Mozilla Thunderbird 78?

tldr: I prefer the Thunderbird 78 interface over the new one. What are the risks of running this older version of Thunderbird?

I got a new laptop, installed Debian and decided to use Thunderbird 78 because I really cannot get used to the current "we need more white space" interface in Thunderbird versions 102 and 115. I added all my mail accounts and everything seems to work fine.

Is there a higher risk for viruses or malware using v78? (Everything else is latest updated Debian stable).

Should I expect problems sending or receiving mail? (I never used its calendar or chat features)

I tried playing with themes and settings and CSS hacks, but none work perfectly and it broke when upgrading from v91 to v102. I use folders extensively and am kinda addicted to the left side of my screen with about 90 visible folders (that turn bold when a mail arrives).