I didn't find a guide for the SM-A136U, but the Spanish site Nadie Me Llama Gallina has one for the SM-A137. Given they both fall under the A13 model number, I suspect there won't be much difference between them. Anyway, here's how to replace that fingerprint sensor/power button.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/samsung-4/samsung-galaxy-a13-sm-a137-1378/flex-de-sensor-de-huella-y-encendido-12476|Manuals / Samsung Galaxy A13 SM-A137 / Fingerprint and Power Sensor Flex Cable - Nobody Calls Me Chicken]
As you might guess, the site is written in Spanish, but if you use it with a browser that includes a translator like Chrome, the guide works just fine no matter what your native language is.
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P.S., A little research shows the A137 is a 4G phone, while your A136U is the 5G model. I still maintain there shouldn't be major differences in the procedure between the two.
I didn't find a guide for the SM-A136U, but the Spanish site Nadie Me Llama Gallina has one for the SM-A137. Given they both fall under the A13 model number, I suspect there won't be much difference between them. Anyway, here's how to replace that fingerprint sensor/power button.
[link|https://www.nadiemellamagallina.com/en/manuales/smartphones-1/samsung-4/samsung-galaxy-a13-sm-a137-1378/flex-de-sensor-de-huella-y-encendido-12476|Manuals / Samsung Galaxy A13 SM-A137 / Fingerprint and Power Sensor Flex Cable - Nobody Calls Me Chicken]
As you might guess, the site is written in Spanish, but if you use it with a browser that includes a translator like Chrome, the guide works just fine no matter what your native language is.