Strict Transport Security - has been updated on LoneSync along with removal of older security methods.
Older security methods were required in tandem with updated security for older devices. As older devices phase out, this requirement becomes much less and therefore shouldn't be a problem for users updating forward.
By moving to strictly Modern Security also helps to increase safety on the internet as a whole. Today there are too many threats on-line and your security is extremely important. Updating is not just for features - keeping on top of App and Device updates is your first device against open-holes that are patched through updates.
Going forward this site will only support modern security, which of course will support all devices which are also supporting modern security. Modern still means you can use devices which are a couple versions back from the latest release, simply keep your browser updated and there shouldn't be any problems.
Modern Security is what more and more sites will move to in 2020, same for Browsers such as Microsoft Edge, Chrome, Safari....all have a time-line of phasing out older security through 2020.