I will write up a summary of ideas suggested in the Ragchew Ramble/Tower Talk net for Friday October 23 2020 when the net has finished.
Here are some resources to check out before that time.
A good summary over-view of the issues involved.
Here is a good overview of antenna strategies that did not work so that you don’t have to discover them yourself.
While using a mobile whip antenna for HF work may appear to be a solution, they are very inefficient with the best being only 12%. The solution may be making a loop antenna. There are two types, voltage and magnetic. This is an article on making a voltage antenna.
Here is an example of an apartment station with a loop antenna suspended on the ceiling.
Another popular solution is the magnetic loop. These antennas are relatively small in size and have an efficiency that is superior to whip antennas at 40 to 60%. The main issue is the need to tune the antenna every time you change frequency with a tunning capacitor attached to the loop. They also generate very high RF voltages so you need to be careful using them. However, they are becoming the solution of choice for hams with limited alternatives.
Here is a demonstration video that shows the steps used to construct a transmitting loop antenna (warning, there are recieving loop antenna designs available on the Internnet and they are unsuitable for transmitting, and can damage your transmitter if used. Only use loop antennas specifically intended for transmitting.)
Here is an instruction for making a magnetic loop antena for 80 and 40 meters.