I'm not a firefox user (edit: currently anyway; more below on that), but the firefox version on openbsd 6.5 is 67.0.4, and firefox-esr 60.8.0 and 60.9.0, for what it's worth. I need to upgrade to obsd 6.6 sometime, and that probably has a later version (checking... I see on the obsd 6.6 packages lists both firefox 69.0.2 and firefox-esr 68.1.0 and 68.2.0. In the last release cycle, obsd has made package upgrades easier between the 6-monthly system releases, but I don't know if that would meet your needs exactly.

For me, the point is as described elsewhere on this discussion (search for "lcall"): obsd is really good at isolation of users, and limiting potential damage by processes within a user's space, which I think of (at least on obsd) much more reliable than what a browser would do alone. So, I do my browsing in a user account that doesn't have access to the most important other things. If I do something like banking, I do that in a separate user account that does only that or only things at that level of security, separately from general browsing. And I mostly have images/javascript turned off when I do general browsing.

In my comment history there is another about why I use Iridium (or chromium sometimes) instead of firefox, with a question where you might know more than I.

(At my site lukecall.net , in the page footer is my email address if you have questions later that I might be able to answer.)

edit: ps: the way I separate users does involve extra work though, but now that the work is done I like it.