However it still takes a lot of effort and most of your free time. You have to be extremely driven to complete such a complex project.
I took a serious "staycation" back in December, and wrote about it here: https://www.reddit.com/r/Coronavirus/comments/fgvbsv/staythe...
During those few weeks, I made what seems like a year worth of progress on several projects. Being able to dive in and focus, for hours at a time without worrying that I had other stuff I should be doing, made all the difference in the world.
Rearranging your week to have one "no-chores no-email" evening, when you just use a single large block of time to immerse yourself in a leisure activity, is worth a try.
This has basically become possible due to cheap and accessible TDCs. Both TI and Ams make them now, designed for gas ultrasound flow sensing. Most of the other components have been readily available for a while (not sure about the APDs, but certainly you could buy stuff from Hamamatsu or Thorlabs/Edmund). ROS makes SLAM quite easy if you have a hardware driver, though the utility that the author made for debugging is very neat.