I’m tagging this as a “me too” but otherwise providing no other useful information or a solution.
I notice the main camera on my Moto G 5G is capped at 1/3 of a second, but my buddy’s LG V20 will go all the way up to 60 seconds using the same version of OpenCamera. (Yes, we both have API2 enabled.) I’d be interested to see if this can be twiddled e.g. with root, or possibly by poking some config file with ADB or something.
mobergmann