Block the sites
BetBlocker Free
A UK registered charity, free forever, no account needed. Blocks roughly 335,000 gambling sites on Windows, Mac, Android and iOS, and you can set a period you cannot cancel. betblocker.org
Gamban
Paid, around $3 a month, and meaningfully harder to bypass. Many state helplines and treatment programs hand out free licences — ask before you pay. gamban.com
Stop yourself reinstalling
Deleting the app is not a block. On iPhone: Settings → Screen Time → Content & Privacy Restrictions → iTunes & App Store Purchases → set Installing Apps to Don't Allow, then have someone else set the passcode.
Block the money
Ask your bank for a gambling block
Card networks file betting merchants under merchant category code 7995. Ask your bank to block MCC 7995. Naming the code gets you past the agent who says it is not possible.
Clear the stored rails
Remove saved cards from each sportsbook, and revoke it under PayPal → Settings → Payments → Automatic Payments. A saved card is the difference between a relapse that takes four seconds and one that takes twenty minutes.
Withdraw the balance first
Self-excluding with money in the account is a common trap — some operators make you contact support to release it afterwards, which means talking to the company you are trying to leave.