Debt vs investing in brokerage

Assuming you've maxed available tax advantaged accounts, what interest rate would you pay down debt versus invest?

I recently took out 3.74% auto loan instead of selling. Mortgage 3.75% and a securities backed line of credit variable at SOFR +1.55% (5.9%).
I currently pay minimums and just let interest accrue on SBLOC. I was paying down SBLOC with minimal dividends spit off from index funds but I stopped when rate dipped back below 6% or so. Now I'm thinking 6.5% is my new threshold to consider paying it down instead of reinvesting dividends. I'd probably get more aggressive and even sell shares to pay off if rate ever exceeds 8%.

As long as rates are below 7% or so, I'd rather borrow for large expenses to stay fully invested and avoid realizing capital gains (prefer to harvest in zero bracket or pass to heirs w stepped.up basis)