did you read the article I linked?

https://pmc.ncbi.nlm.nih.gov/articles/PMC4054695/

Decreased sleep duration in meditators during periods of intensive practice, such as multiday silent retreats is a well-known phenomenon²⁷ and is considered a sign of meditative proficiency and progress.¹⁹ Kornfield¹⁶³ documented decreased sleep duration in Theravada Vipassana meditators on 3-month retreats (12–15 h of meditation/day) compared to a control group who meditated 1–2 h/day. Seventy percent of the retreat participants reported an average 2 h decrease in sleep duration in comparison to 10% of controls, who also reported increases in sleep duration (10%). The periods of sleep decrease were associated with periods of greatest self-reported and teacher-observed mindfulness.

…

A recent study examined sleep duration of meditators in daily life, using objective, EEG-based measures of sleep in a much larger sample. This cross-sectional study¹⁶⁵ recorded single-night polysomnographic sleep studies (high-density EEG) in long-term (8700 average lifetime meditation hours) Tibetan and Theravada Buddhist meditators and age- and gender-matched non-meditating controls. The meditators had a significantly reduced total sleep time (6.2 vs. 6.7 h, P= 0.001) as well as increased minutes of wake after sleep onset (74 vs. 44 min, P =0.003) compared to controls.

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Thus, the point when meditation practice no longer produces drowsiness and sleep, but instead engenders increased and sustained wakefulness, may be an indicator of the neuroplastic changes that signify meditative proficiency. In this sense, “awakening” is not a metaphor, but rather an iterative process of neuroplastic modifications and increased efficiency that supports a new level of perceptual sensitivity and insight.

tl;dr enough skillful meditation reduces your sleep

Since I experience this reduction in sleep as unwanted and disruptive, I call it insomnia - but call it what you want, it’s increased wakefulness and decreased sleep.

Not only does the effect last (as long as you continue to practice enough hours of meditation skillfully), it’s very common and well known among Buddhist monks who meditate that you stop sleeping, even remaining aware during sleep:

In many Tibetan Buddhist¹⁶¹ and also non-Buddhist traditions,¹⁶² the goal of cultivating of vigilant awareness in every waking moment is extended beyond the waking state to sleep states as well. One teacher instructs “When you fall asleep, you are asleep with virtually full awareness.”¹⁶¹ Several studies have described meditators’ self-reports of ongoing conscious awareness during sleep.^162,163 In support of such increased wakefulness during sleep, several polysomnographic sleep studies have found greater cortical arousal during sleep in meditators, including increased stage-1 sleep, alpha-theta (wake-like) EEG, arousals, reduced slow-wave sleep,^144,162,164 and increased gamma.¹⁶⁵

The amount of sleep of proficient meditators according to Buddhist texts is around 4 hours a night, with observed amounts of meditators in retreat of 1.5 - 3 hours:

In a qualitative study in our laboratory, a meditator who had completed a 3-month Tibetan-style shamatha retreat (12–15 h/day), reported that for the first 2 weeks of the retreat, her sleep duration initially increased to 8 h/night before gradually diminishing to 1.5–3 h/night by the eighth week. Buddhist texts suggest a nocturnal sleep time among proficient meditators of approximately 4 hours.¹⁹

Furthermore, I have no insomnia without mediation - when I meditate regularly I have difficulty falling asleep and maintaining a normal sleep schedule, many nights not sleeping more than 4 - 6 hours. When I stop meditating, I go back to sleeping 8 - 10 hours a night. This happens every time I go back to meditating, and stops every time I stop. It is clearly caused by the meditation.

The meditation is not causing insomnia because of increased contemplation of mental health issues, like therapy might cause insomnia - I do not experience the insomnia as anxious rumination or anything like that. Instead it feels like a generalized hyperarousal, like I took a stimulant, or if you vigorously exercise too late on a sunny day.

I can spend hours counting sheep and it’s too engaging, so I try to manufacture the most mundane and boring situations possible. I would often even remain awake during dreams, it’s just difficult to fully lose consciousness. Usually I would lose consciousness only after many hours of lying awake, usually sometime like 2 - 4 in the morning.

I’m not sure why you are so confident that insomnia is not a side effect of meditation. How frequently and how much do you meditate, and what style of meditation do you do? I think these things could make a difference in your experiences, e.g. I suspect open awareness practices are less likely than concentration practices in terms of creating increased wakefulness.