There is more BTC on Polygon than on the Lightning Network!
Currently there is over 25,000 BTC on the Polygon network as WBTC, most of it is being used as productive asset deposited in liquidity pools, farming contracts etc. This 25K BTC represents 0.13% of BTC's entire supply.
However the much talked about Lightning Network only has around 1450 BTC.
This means Polygon can virtually act as L2 or L3 for BTC.
Source for WBTC on Polygon supply: https://polygonscan.com/token/0x1bfd67037b42cf73acf2047067bd4f2c47d9bfd6 (25,449.23844 WBTC)
Source for BTC on LN: https://1ml.com/ (1,467.46 BTC)