It should be noted that this is the way a specific app parses the notes (a feature of the app itself) and not part of (a function of?) the podcast’s metadata.
Edit for clarification:
Compare the extracted metadata of the most recent episode (286) with the extracted metadata of a known working chapters episode (281).
Episode 286
;FFMETADATA1
title=Destination Linux 286: We're Hardware Addicts For Linux Laptops
encoded_by=Destination Linux Network
album=Destination Linux
genre=Podcast
copyright=2022 Destination Linux Network
TOPE=Destination Linux Network
TGID=http://destinationlinux.fireside.fm/286
publisher=Destination Linux Network
artist=Destination Linux Network
date=2022
encoder=Lavf58.76.100
Episode 281
;FFMETADATA1
title=Destination Linux 281: 281: Linux Alternatives to Adobe Photoshop, Premiere Pro, Illustrator & more
encoded_by=Destination Linux Network
album=Destination Linux
genre=Podcast
copyright=2022 Destination Linux Network
TOPE=Destination Linux Network
TGID=http://destinationlinux.fireside.fm/281
publisher=Destination Linux Network
artist=Destination Linux Network
date=2022
encoder=Lavf58.76.100
[CHAPTER]
TIMEBASE=1/1000
START=0
END=56975
title=Welcome to DL 281
[CHAPTER]
TIMEBASE=1/1000
START=56975
END=414975
title=What Michael has been up to
[CHAPTER]
TIMEBASE=1/1000
START=414975
END=892975
title=Community Feedback from Jack
[CHAPTER]
TIMEBASE=1/1000
START=892975
END=975975
title=DigitalOcean Cloud Platform
[CHAPTER]
TIMEBASE=1/1000
START=975975
END=1243975
title=Linux Alternatives to Adobe Photoshop Premiere Pro Illustrator & more
[CHAPTER]
TIMEBASE=1/1000
START=1243975
END=1936975
title=Adobe Photoshop Alternatives on Linux
[CHAPTER]
TIMEBASE=1/1000
START=1936975
END=2324975
title=Adobe Illustrator Alternatives on Linux
[CHAPTER]
TIMEBASE=1/1000
START=2324975
END=2426975
title=Adobe InDesign Alternatives on Linux
[CHAPTER]
TIMEBASE=1/1000
START=2426975
END=3176975
title=Adobe Premiere Pro Alternatives on Linux
[CHAPTER]
TIMEBASE=1/1000
START=3176975
END=3377975
title=Adobe Lightroom Alternatives on Linux
[CHAPTER]
TIMEBASE=1/1000
START=3377975
END=3744975
title=Adobe Dreamweaver Alternatives on Linux
[CHAPTER]
TIMEBASE=1/1000
START=3744975
END=3867975
title=Bitwarden Password Manager
[CHAPTER]
TIMEBASE=1/1000
START=3867975
END=4137975
title=Murena One Smartphone & /e/OS
[CHAPTER]
TIMEBASE=1/1000
START=4137975
END=4374975
title=Linux Gaming: AQtion
[CHAPTER]
TIMEBASE=1/1000
START=4374975
END=4427975
title=Software Spotlight: Cider (iTunes on Linux)
[CHAPTER]
TIMEBASE=1/1000
START=4427975
END=4498975
title=Tip of the Week: . equals current directory
[CHAPTER]
TIMEBASE=1/1000
START=4498975
END=4549975
title=Linux Events
[CHAPTER]
TIMEBASE=1/1000
START=4549975
END=4696775
title=Outro