Although I am not an ambitious SOTA chaser my station and hidden antenna may not be representative.
My solution can therefore be rather a (further) confirmation that an imperfect antenna is much better than no antenna.
Since I was allowed to use a beam antenna only for the first 7 years and then had to use indoor antennas in the last 37 years, I was able to experiment and learn a lot with them (also in drilling long holes through apartment walls and ceilings, hi).
The following rough statistics may give an idea about what is possible (in CW …) with such small indoor antennas as indicated below:
SOTA Associations and regions worked: 181
WAE Countries worked: 49
DXCC Countries worked: 209
Main: Elecraft K3/100, K-POD, P3
Backup: Elecraft K2/100
Receive only: Elecraft K2/10 with IF buffer amplifier, P3
Special purposes/experiments: ICOM IC-706MKIIG (the only rig with a mic connected…)
Keyer: Logikey K-5
Paddle: Begali Sculpture
SWR&Power Meter: Kenwood SW-200
Wattmeter/Dummy Load: Drake W7/DL1000
Remote ATU: LDG Z11ProII (at the feed point of the doublet)
Remote active loop amplifier: Bonito ML200 (at the vertical loop)
Power supply: Diamond GSV3000 (2x)
Main: Indoor Doublet 2x4.90 m, angled several times, usable from 80 to 6 m
Receive only: Indoor vertical loop 6.40 m, around shack window