It looks the problem is missing firmware from your dmesg output. Can you do the following.
1. cd /var/cache/apt/archives
2. sudo dpkg -i linux-firmware_1.173.20_all.deb
3. Reboot
Then share the output of the following again.
Code:
ip a
dmesg | grep iwlwifi
Actually we just downgrade from 1.187.20 to 1.173.20
Here the results:
[ 6.229381] iwlwifi 0000:00:14.3: enabling device (0000 -> 0002)
[ 6.259477] iwlwifi 0000:00:14.3: loaded firmware version 46.4d093a30.0 op_mode iwlmvm
[ 6.337447] iwlwifi 0000:00:14.3: Detected Intel(R) Dual Band Wireless AC 9460, REV=0x318
[ 6.350055] iwlwifi 0000:00:14.3: Microcode SW error detected. Restarting 0x0.
[ 6.350061] iwlwifi 0000:00:14.3: Not valid error log pointer 0x00000000 for Init uCode
[ 6.350075] iwlwifi 0000:00:14.3: Fseq Registers:
[ 6.350078] iwlwifi 0000:00:14.3: 0x9C1777AD | FSEQ_ERROR_CODE
[ 6.350081] iwlwifi 0000:00:14.3: 0xDDBFD5DF | FSEQ_TOP_INIT_VERSION
[ 6.350084] iwlwifi 0000:00:14.3: 0xE7157E5B | FSEQ_CNVIO_INIT_VERSION
[ 6.350087] iwlwifi 0000:00:14.3: 0x197DE7EC | FSEQ_OTP_VERSION
[ 6.350090] iwlwifi 0000:00:14.3: 0x9C904801 | FSEQ_TOP_CONTENT_VERSION
[ 6.350093] iwlwifi 0000:00:14.3: 0x2EE51BC8 | FSEQ_ALIVE_TOKEN
[ 6.350104] iwlwifi 0000:00:14.3: 0x96FBD6F3 | FSEQ_CNVI_ID
[ 6.350107] iwlwifi 0000:00:14.3: 0x5C400CDB | FSEQ_CNVR_ID
[ 6.350110] iwlwifi 0000:00:14.3: 0x01000100 | CNVI_AUX_MISC_CHIP
[ 6.350145] iwlwifi 0000:00:14.3: 0xA5A5A5A2 | CNVR_AUX_MISC_CHIP
[ 6.350214] iwlwifi 0000:00:14.3: 0xA5A5A5A2 | CNVR_SCU_SD_REGS_SD_REG_DIG_DCDC_VTRIM
[ 6.350282] iwlwifi 0000:00:14.3: 0xA5A5A5A2 | CNVR_SCU_SD_REGS_SD_REG_ACTIVE_VDIG_MIRROR
[ 6.350460] iwlwifi 0000:00:14.3: SecBoot CPU1 Status: 0xa5a5a5a2, CPU2 Status: 0xa5a5a5a2
[ 6.350462] iwlwifi 0000:00:14.3: Failed to start INIT ucode: -5
[ 6.350464] iwlwifi 0000:00:14.3: Collecting data: trigger 16 fired.
[ 6.596291] iwlwifi 0000:00:14.3: Firmware not running - cannot dump error
[ 6.609987] iwlwifi 0000:00:14.3: Failed to run INIT ucode: -5