i avoid payment portals whenever i can. my credit union has an online bill pay using ACH services and sometimes its a little clunky to find the biller but i eventually find them all and get them added. usually everything is available on any paper bill (account number, address, etc)
it bypasses all the bullshit convenience fee nonsense and keeps me from allowing like a dozen screwball companies to have access to my financial info.
and i keep that bank account with those billers specifically at a low balance. it is only for paying known bills and won't overdraft.
my family acts like im paranoid, a nerd, and a cheapskate, but all those convenience fees add up. and fuck the risk. i also like having all my payment records in a single transaction list.