I see firefox in the list of available packages (which list is something like 8000 long, last I recall). Iridium is also available (like Chrome but seems usually a slightly older version, with enhanced privacy like not sending info to Google). Iridium + pledge/unveil have been appealing to me, though I keep Chromium on hand in case something doesnt work right.
Firefox may be there, but is it the ESR version and is that up to date? OpenBSD does not seem to update ports for the -release branch, so that doesn't really work for me as I want the latest security fixes from the browser vendor.
Same goes for Chromium. I don't mind missing features. What I do mind is being behind on security patches.
What's the point of using OpenBSD (which is security focused) as a workstation when I can just be pwned by the latest browser bug?
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.