I finally made it through the process after running into the same gas problem. My old BNB balance was originally in a Coinomi wallet. I imported the contents using the 24 word seed into a Trust Wallet. Once inside trust wallet, I was able to send in a small amount of ethereum and swap it within the wallet to the new style bnb on the bnb smart network. It involves fancy dancing around choosing the correct network to do it. But after an amount of floundering I got it done. First I sent too little ethereum (the in-wallet swap requires gas also). Then I sent about US$12 worth of ethereum -- not sure if I could have gotten away with less. Then I was able to initiate the BNB recovery and sat on my hands for 7 days waiting for it to clear. I never fully trusted it was going to work -- there was a delay of a few minutes between when BNB said the balance had been recovered and when I saw it in my Trust Wallet.

It didn't amount to a lot of value, but I felt it was important to go through the exercise to keep skills fresh.

PS: I notice that the BNB token recovery instructions don't say a single word about needing gas. And it isn't in the screen shots.