When adding adapter: ezsp to the serial field, and attempting to start the add-on, this is what the logs say:
[14:41:03] INFO: Preparing to start...
[14:41:03] INFO: Socat not enabled
[14:41:03] INFO: Starting Zigbee2MQTT...
Starting Zigbee2MQTT without watchdog.
[2024-07-16 14:41:05] info: z2m: Logging to console, file (filename: log.log)
[2024-07-16 14:41:05] info: z2m: Starting Zigbee2MQTT version 1.39.0 (commit #unknown)
[2024-07-16 14:41:05] info: z2m: Starting zigbee-herdsman (0.50.1)
[2024-07-16 14:41:05] warning: zh:ezsp: Deprecated driver 'ezsp' currently in use, 'ember' will become the officially supported EmberZNet driver in next release. If using Zigbee2MQTT see https://github.com/Koenkk/zigbee2mqtt/discussions/21462
[2024-07-16 14:41:15] error: zh:ezsp:uart: --> Error: Error: {"sequence":-1} after 10000ms
[2024-07-16 14:41:15] error: zh:ezsp:ezsp: Connection attempt 1 error: Error: Failure to connect
at SerialDriver.resetForReconnect (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/ezsp.ts:347:19)
at SerialDriver.emit (node:events:517:28)
at /app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/uart.ts:348:22
at Queue.execute (/app/node_modules/zigbee-herdsman/src/utils/queue.ts:35:20)
at SerialDriver.openSerialPort (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/uart.ts:108:13)
at SerialDriver.connect (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/uart.ts:63:13)
at Ezsp.connect (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/ezsp.ts:353:17)
at Driver.startup (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/driver.ts:164:13)
at Controller.start (/app/node_modules/zigbee-herdsman/src/controller/controller.ts:129:29)
at Zigbee.start (/app/lib/zigbee.ts:63:27)
[2024-07-16 14:41:30] error: zh:ezsp:uart: --> Error: Error: {"sequence":-1} after 10000ms
[2024-07-16 14:41:30] error: zh:ezsp:ezsp: Connection attempt 2 error: Error: Failure to connect
at SerialDriver.resetForReconnect (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/ezsp.ts:347:19)
at SerialDriver.emit (node:events:517:28)
at /app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/uart.ts:348:22
at Queue.execute (/app/node_modules/zigbee-herdsman/src/utils/queue.ts:35:20)
at SerialDriver.openSerialPort (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/uart.ts:108:13)
at SerialDriver.connect (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/uart.ts:63:13)
at Ezsp.connect (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/ezsp.ts:353:17)
at Driver.startup (/app/node_modules/zigbee-herdsman/src/adapter/ezsp/driver/driver.ts:164:13)
at Controller.start (/app/node_modules/zigbee-herdsman/src/controller/controller.ts:129:29)
at Zigbee.start (/app/lib/zigbee.ts:63:27)