Bipolar PROMs were initially used mainly to store microprograms for CPUs with microprogrammed control and for implementing various kinds of programmable logic, in which role they were later replaced by PLAs, then by PALs.
I do not think that there has ever been any kind of computer that has stored in bipolar PROMs programs that were usable during normal operation, except perhaps some kind of embedded controllers designed before microprocessors become widespread, together with their associated EPROMs.
By the time when the Intel EPROMs like 1702 and 2708 have appeared (with a capacity of 256 bytes, then of 1 kbyte), typical bipolar PROMs had capacities of either 32 bytes or 128 bytes.
In that space you could put at most some kind of initial loader that would load a real bootstrapping program from something like a punched-tape reader. This kind of solution was used in some minicomputers, replacing the introducing of such an initial loader from console keys, by the operator. Such minicomputers were still at least an order of magnitude more expensive than the first computers with microprocessors, mainly due to the expensive peripherals required for a working system.
The Altair 680 had sockets for four 256 byte PROMs. One was for the debugger, but a popular option for the other three was the VTL-2 (very tiny language) interpreter. Pretty amazing that they fit a Basic-like language in just 768 bytes, though implementing some language in the 510 byte boot sector has become a popular hobby.