How can I fix this issue(Linux tools preferred)?
You can use SP Flash Tool. You need MediaTek MT65xx USB VCOM Preloader USB Drivers for it. If you care about data, you should make a full rom dump (or at least nvdata metadata oemkeystore and userdata partition). You need a scatter file for this. A scatter file you can create with WwR MTK v2.30.
If fastboot is working, you can try "fastboot format:ext4 cache" to fix bootloop. You can try to port a TWRP and "fastboot boot recovery.img" then you get full access via adb in recovery (and if metadata is still intact it will hopefully decrypt userdata).
If the bootloop is caused by flashing TWRP, install Universal Disable_Dm-Verity_ForceEncrypt.zip to disable the dm-verity boot chain validation.