Honestly repairs would be recommended, you always have the option of visiting your local uBreakiFix for walk-in repair opitons: https://www.ubreakifix.com/locations
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My Galaxy S20 FE 5G Power button has also just fallen off. No damage to the phone; has been in its Samsung silicon cover since day of purchase. Took the cover off to clean the phone and noticed the power button had fallen off. Luckily I found the button. The cover actually holds the button in place. Unfortunately I am not able to take the phone back to where it was purchased. Hopefully, Samsung South Africa will honor the warranty, they have a tendency not to honor warranties if the phone was purchased in another county.