After a water main line repair on our street, our hot water stream for the bathtub suddenly is very weak. Could the pipe be clogged by debris?
Yes debris could be plugging the bathtub valve (easy check other faucets working properly? )
Could the trickle of water speed up the mineral deposits cause this (if you have been doing it constantly for years,,, ok not to this level)
Debris are probably plugging the orifices in the valve. Many valves can be disassembled then water flowed pushing out the debris that are causing the blockage.
Single handle or washer-less faucet. Turn the water off pull the cartridge, the tricky part now flush the valve by turning the water on for a second pushing the debris out of the valve. If the valve is recessed in the wall aluminum foil or even heavy card stock paper around the valve into the tub to catch the water reduces the mess. Clean out the cartridge some are not that expensive to replace and you get new seals. Reassemble and turn water back on.
I have done this on multiple valves. Washer based valves same process remove valve stem and flow water to flush debris out.
If a shower head is plugged don’t forget it could be just the head it self, but tub spigots are usually wide open after the valve so the blockage is normally at the valve(s)