The Sex Reassignment Surgery (SRS) and Transgender Hormone Therapy (THT) articles on Baike wiki includes the current situation in China. From what I’ve read in these two articles, THT is less “standardized” than SRS, and the former cannot be used as a basis to change your legal sex.

What I mean by “standardized” is that the National Health Commission has published standards for SRS in 2017 and updated them in 2022, the same cannot be said for THT. Here are the criteria in 2017 and 2022 for someone who wants to undergo SRS: (translated with DeepL)

2017:

性别重置技术管理规范（2017年版） – 三、技术管理基本要求 – （四）手术前手术对象应当满足以下条件：

1. 对性别重置的要求至少持续5年以上，且无反复过程。
2. 术前接受心理、精神治疗1年以上且无效。
3. 未在婚姻状态。
4. 年龄大于20岁，具备完全民事行为能力。
5. 无手术禁忌证。

Translation: Code of Technical Management for Gender Reset (2017 Edition) - III. Basic Requirements for Technical Management - (d) Pre-surgical surgical candidates should fulfill the following conditions:

1. The [request/need] for gender reset has lasted for at least 5 years without a recurrent process.
2. Received psychological and psychiatric treatment for at least 1 year prior to the surgery and is ineffective.
3. Not in the state of marriage.
4. Be older than 20 years old and have full capacity for civil behavior.
5. No contraindications to surgery.

2022:

国家限制类技术临床应用管理规范（2022 年版） – G05 性别重置技术临床应用管理规范（2022 年版） – 三、技术管理基本要求 – （四）手术前手术对象应当满足以下条件：

1. 对性别重置的要求至少持续 5 年以上，且无反复过程。
2. 未在婚姻状态。
3. 年龄满 18 岁，具备完全民事行为能力，有能力完成性别重置序列治疗。
4. 无手术禁忌证。

Translation: National Code of Practice for Clinical Application of Restricted Technologies (2022 Edition) - G05 Code of Practice for Clinical Application of Gender Reset Technologies (2022 Edition) - III. Basic Requirements for Technical Management - (d) Pre-surgical surgical objects should fulfill the following conditions:

1. The request for gender reassignment has lasted for at least five years without a recurring process.
2. Not in the state of marriage.
3. Have reached the age of 18, have full capacity for civil behavior, and have the ability to complete the gender reassignment sequence treatment.
4. No contraindications to surgery.

Note that the updated criteria in 2022 removed the need for previous psychological and psychiatric treatment, and lowered the age requirement from 20 to 18.

There were two nationwide studies on the transgender community, conducted in 2017 and 2021, and problems with medical support in China was mentioned in the published findings.

Back to the question about access to estrogen, since there does not seem to be any national standard for THT, and 雌二醇 (Estradiol) is prescription medication, I would guess that it is indeed hard to get estrogen.

The user also mentioned that this is the only thing stopping them from moving to China, I think they’re underestimating the challenges in emigrating to any foreign country in general, especially a country with a strong national identity like China.